Site-specific integration of corynephage phi 16: construction of an integration vector

phi 16, a temperate phage induced from Corynebacterium glutamicum ATCC 2179 2, lysogenizes its host via site-specific recombination. The phage attachme nt site, attP, was located to a 6.5 kb BamHI fragment of the phi 16 genome. This fragment also contained phi 16 integrative functions. The minimal pha ge DNA fragment required for integration was defined. This 1630 bp region c ontained a large open reading frame, int, encoding a protein of 416 amino a cids with similarity in its carboxyl-terminal domain to tyrosine recombinas es and particuliarly to the Xer recombinases. The comparison of the nucleot ide sequences of attB, attL, attR, and attP identified a common 29 bp seque nce, the core sequence. It lies 11 bp downstream of the 3' end of the integ rase gene. phi 16 integrase was shown to catalyse site-specific integration in trans to attP with an efficiency of 5 x 10(3) integrants per pg DNA. Th e integrating fragment catalysed integration in several Corynebacterium str ains that are not infected by phi 16. thus enlarging the host spectrum of i ntegrating vectors derived from phi 16. In these strains, the phi 16 attB s ite was located in a conserved intergenic region and lies downstream of a c lp gene.